Orsay, France, May 17, 2010 - Immutep S.A. announced today that
the final results from its Phase I/II chemoimmunotherapy clinical
trial in metastatic breast carcinoma will be shown in an oral
presentation at the 46th Annual Meeting of the American Society of
Clinical Oncology (ASCO). The ASCO meeting will be held at
McCormick Place in Chicago from June 4 through June 8, 2010.

The oral presentation is entitled "First-line chemoimmunotherapy
in metastatic breast carcinoma: effect of a combination of
paclitaxel and LAG-3Ig (IMP321), a novel MHC class II agonist, on T
cell responses and anti-tumor activity” and is scheduled for
Tuesday, June 8 from 11:45 to 12 a.m. CDT in room E354a.

IMP321 is a T cell immunostimulatory agent. Repeated IMP321
injections lead to strong anti-tumour T cell responses. In
synergistic combination with first-line chemotherapy, IMP321 may
increase the clinical response rate. This therapeutic strategy is
called chemoimmunotherapy.

The study was carried out in three cancer centres in the Paris
region. The lead centre was the René Huguenin Cancer Centre
in Saint Cloud. The other centres were Tenon Hospital and the
Georges Pompidou European Hospital in Paris.

The abstract can be accessed after May 20, 2010 through the ASCO
website, http://www.asco.org and will be accessible from Immutep's
website at http://www.immutep.com after the presentation.

Notes to Editors

ImmuFact(R) - T cell Immunostimulatory Agent for amplifying the
T cell response ImmuFact(R) IMP321 is a first-in-class
antigen-presenting cell (APC) agonist. It is a soluble form of the
LAG-3 ("lymphocyte activation gene-3") T cell surface receptor that
binds, with high affinity, to MHC (“major histocompatibility
complex”) class II molecules on APC such as monocytes and
dendritic cells. Repeated IMP321 injections lead to strong
anti-tumour CD8 T cell responses in cancer patients especially in
combination with chemotherapy.

Metastatic Breast Cancer and Chemoimmunotherapy Metastatic
breast cancer remains incurable. The failure of current approaches
is generally attributed to the outgrowth of breast tumour cells
that are inherently resistant to standard treatments. Manipulating
the immune system to recognize and eradicate breast tumour cells is
a highly attractive alternative approach to disease management.
Active immunization offers multiple theoretical advantages over all
other therapies, including low toxicity. The sustained antitumour
effect due to immunological memory would obviate the requirement
for prolonged, repetitive cycles of therapy.

The objective of chemoimmunotherapy is to amplify natural
pre-existing T cell responses specific for any known or unknown
tumour antigen and to recruit and amplify new tumour-specific T
cell responses resulting from the use of cytotoxic drugs. The
direct cytolytic effect of some cytotoxic drugs, such as
paclitaxel, can enhance antigen presentation by inducing tumour
cell apoptosis. This mechanism of therapeutic synergy has been
shown with cyclophosphamide, doxorubicin, or paclitaxel when given
with dendritic cell–based vaccines. Until 8 years ago, it was
thought that the T cell depletion caused by chemotherapy would make
immunotherapy ineffective. However it has now been shown that, on
the contrary, the vigorous T cell repopulation following depletion
can be directed against the tumour.

Soluble LAG-3 protein is a prognostic factor in breast cancer
ImmuFact IMP321 is closely related to the soluble form of the LAG-3
(Lymphocyte Activation Gene-3) protein which is a prognostic
indicator for survival in breast cancers expressing oestrogen or
progesterone receptors. This was shown is a study carried out by
researchers at the René Huguenin Cancer Centre and Pr.
Frédéric Triebel when he was at the Pharmacy Faculty
of University Paris 11. These results paved the way for the current
clinical trial. (Immutep Press Release No 6, April 2006)

Centre René Huguenin de Lutte contre le Cancer The
René Huguenin Centre for the Fight against Cancer is a
comprehensive cancer centre that treats more than 3,000 new cases
of cancer each year, with more than 2,000 new cases of breast
cancer. It has a medical staff of 66 practitioners. Besides
participation in therapeutic trials, the Centre has developed
special expertise in the field of tumorigenesis and
pharmacogenetics of breast cancers. Professor Jean-Nicolas Munck is
the Directeur-Général of the Centre.

Immutep S.A. Immutep S.A. is a biopharmaceutical company
developing immunostimulatory factors for the treatment of cancer
and chronic infectious diseases and immunomodulatory therapeutic
antibodies for the treatment of cancer or autoimmune disease. The
Company's technologies are based on the LAG-3 immune control
mechanism that mediates T cell immune responses.

ImmuFact(R) - Clinical Development More than 600 s.c. injections
of IMP321 have been administered to date in Europe and the USA at
doses up to 30 mg with no clinically significant drug-related
adverse events. A Phase I trial in metastatic renal cell carcinoma
with IMP321 alone has been completed. A Phase I/II trial in
metastatic breast cancer combining IMP321 with weekly paclitaxel in
a chemo-immunotherapy protocol has been completed
(http://clinicaltrials.gov/ct/gui/show/NCT00349934?order=1
). Three Phase I/II clinical trials are in progress: in pancreatic
cancer combining IMP321 with gemcitabine in chemoimmunotherapy
(http://www.clinicaltrials.gov/ct2/show/NCT00732082?term=07-0265&rank=1
), a disease-free melanoma study with IMP321 as a therapeutic
vaccine adjuvant to peptide antigens and a
lympho-depletive/adoptive transfer metastatic melanoma study.